FIELD OF THE INVENTION
The invention concerns a process for the galvanic precipitation of zinc deposits and/or zinc-alloy deposits on a metallic surface, working with an aqueous acid electrolyte which contains at least one zinc salt and at least one high-gloss agent.
Different processes for the galvanic precipitation of zinc deposits and zinc alloy deposits are known from in practice. To this extent, comparable acid zinc electrolytes or zinc-alloy electrolytes are also known. Coating of metallic surfaces is usually carried out on the basis on the good anti-corrosion effect achieved by the zinc or zinc-alloy layers. It is often also desirable for the zinc or zinc-alloy coats to have a glossy surface and fulfil ornamental purposes. High-gloss agents are added to the electrolytes for this purpose, which, interacting as needed with other electrolytic components, produce the gloss on the zinc or zinc-alloy coats. In the processes mentioned above known in practice, aromatic carbonyl compounds, particularly benzylacetone or benzophenone as well as o-chlorobenzaldehyde, are used. The high-gloss agents are usually employed in a solution of alcohol, particularly methanol. Special safety precautions are necessary in the manufacture, transportation and storage of these solutions, because of their high flammability and toxicity. The disadvantage is unnecessary expense. The high-gloss agents are also used in higher boiling solvents, in butyl glycol for example, which bring disadvantages of a physiological nature. Since the solubility of the familiar high-gloss agents mentioned is very low, they must be solubilized with high concentrations of wetting agents in the aqueous electrolytes. This is also complicated and costly.